Integrated circuits (IC's) are known to include a substrate, one or more dielectric layers on the substrate, and one or more metal layers supported by a corresponding dielectric layer. The metal layers are fabricated in such a way to produce on-chip components such as resistors, transistors, capacitors, inductors, et cetera. How an on-chip component is fabricated, as well as the number of dielectric layers and metal layers, minimum and maximum metal track sizes, and spacing between metal tracks, are dictated by the technology used and corresponding foundry rules governing the fabrication of integrated circuits using such technology.
For example, CMOS technology is readily used for cost effective integrated circuits. Foundries that manufacture CMOS integrated circuits provide rules governing the number of dielectric layers and metal layers, minimum and maximum metal track sizes, spacing between the metal tracks, fabrication options, and other aspects of integrated circuit production. The fabrication options include adding a P-well layer, adding a field oxide layer, adding a poly-shield, et cetera.
It has become conventional wisdom, (i.e., a de-facto standard) among on-chip inductor designers that the quality factor (i.e., the measure of a component's, or circuit's, ability to provide a large output at resonant frequency and the frequency selectivity of the component or circuit) is maximized by including a poly-shield with a P-well layer and a field oxide layer. By designing 8 to 10 nano Henry on-chip inductor in accordance with conventional wisdom, a quality factor of about 8.07 to 8.70 can be obtained at 2.4 gigahertz. While such inductors may be acceptable for some applications, improving the quality factor of on-chip inductors improves performance in such applications and allows on-chip inductors to be used in many other applications currently beyond the reach of conventional on-chip inductors.
Therefore, a need exists for an on-chip inductor that has an improved quality factor with respect to current on-chip inductors and a need exists for a method of manufacture thereof.